Where is the file directory of blender modifiers python code?
Modifiers need to be able to deal with a huge volume of data, which is one of the reasons why Blender has them implemented in C.

In short, there is no Python code for the modifiers.

If you modify the C code for the modifiers &amp; build your own Blender, then yes, there is a chance that Blender will crash (same as any other modification of its code; this is not limited to modifiers).